Problem: A bag contains $9$ red balls, $5$ green balls, and $5$ blue balls. If a ball is randomly chosen, what is the probability that it is not red?
There are $9 + 5 + 5 = 19$ balls in the bag. There are $9$ red balls. That means $19 - 9 = 10$ are not red. The probability is $ \frac{10}{19}$.